Effects of Precured Fillers with differently Treated Nano-particles on Composites

Objective: To enhance the physical and mechanical properties of dental composites, nano-particles were added to the composite as much as possible. The purpose of this study was to evaluate the effect of nano-particles treated with different functional groups on the precured filler system and dental composites. To investigate the effects above mentioned, polymerization behavior and optical properties were compared.

Method: Precured fillers were formulated with three different functional groups (-OH, -CH3, or methacrylate). 80 parts of nano-particle, 20 parts of bis-GMA, and 0.5 parts of BPO were mixed and heat-polymerized at 130 °C, then grind into fine particles (10 µ) to produce the precured filler (PCF1, PCF2, PCF3). Three experimental composite resins (PCFR-1, PCFR-2, PCFR-3) were made with 20 wt% of resin matrix (bis-GMA, TEGDMA, catalysts, stabilizer), 74 wt% of inorganic filler and 6 wt% of precured filler. Control group (CTL) was prepared with 78 wt% of inorganic filler. Flexural strength, polymerization shrinkage, depth of cure, and opacity were tested.

Results: Flexural strength of composites with precured fillers (100-112 MPa) showed similar flexural strength to control group (118 MPa). Depth of cure was not affected by the addition of precured fillers. Polymerization shrinkage, however, was significantly reduced from 2.49% to 2.00% with adding precured fillers. Experimental groups also showed more translucent than the control group.

Conclusion: Precured filler system may affect the polymerization behavior and optical properties of dental composites.

Acknowledgement: This study was supported by Components and materials technology development program, MOCIE, Republic of Korea (Grant Number:0701DG10271)